This invention relates to a shaped explosive charge, a method of blasting using the shaped explosive charge and to a kit to make the shaped explosive charge.
Explosives are used widely in the mining industry to wrest ore from the ground. They are used also in other applications, however, to fracture solid masses, for example rocks, boulders and concrete. In mining, ore is extracted from a general body of rock by blasting the rock. This is known as primary rock blasting. The result of this primary rock blasting is a number of pieces of rock of varying sizes. Generally, at least 1-5% of this rock is oversized in that it cannot be handled or processed by standard equipment or techniques. The oversized rock must then be subjected to one of three further steps before it is rendered manageable. These steps are collectively known as secondary breakage.
In the first of these steps an amount of explosive is placed at a point on the periphery of the rock mass. It is often fixed to the rock mass or confined by surrounding it with sealer to form a "mudcap". The explosive is then detonated to further reduce the rock mass into pieces that are easier to handle. The main disadvantages of this method are that it is an inefficient use of energy and is violent in terms of airblast and flyrock.
The second method of breaking down oversized pieces of rock is to bore a channel in the rock mass and then to place explosives in the hole and then to explode them. This method, however, is labour intensive as each targeted rock mass has to be worked on and expensive and bulky machinery is required to bore the holes, and it is time consuming. This method of blasting can also produce dangerous flyrock.
The last method is that of mechanical breakage where the oversized pieces of rock are broken by drop weights and other mechanical means to more manageable pieces. The disadvantages of this method are that bulky and expensive machinery is needed to break the oversized rock one at a time, and the machinery is subject to large amounts of stress and wear and tear and is thus also expensive to maintain.